Unseeded Jelena Ostapenko fought back to stun third seed Simona Halep and become Latvia's first Grand Slam champion at the French Open.
The 20-year-old trailed by a set and was 3-0 down in the second to Halep - who would have become world number one with a win - but prevailed 4-6 6-4 6-3.
Ostapenko, ranked 47th, had never won a Tour-level title before and was playing in only her eighth Grand Slam.
She is the first unseeded woman to win at Roland Garros since 1933.
Halep, 25, was playing in her second French Open final, after losing in three sets to Maria Sharapova in 2014.
She had been the tournament favourite this time in the absence of Serena Williams, but again missed out on a first major title.
Attack beats defence for Ostapenko
Ostapenko's carefree attacking tennis ultimately proved too strong for the consistency and experience of Halep, with the favourite helpless by the closing stages.
The difference in approach was clear in the final statistics, Ostapenko ending with 54 winners and 54 errors, to Halep's eight winners and 10 errors.
Halep looked to have ridden out the storm after twice coming back from a break down to take the first set, with Ostapenko giving it up with her 23rd error and swiping her racquet in frustration.
The Romanian had played the percentages, with just one winner and two errors, and she looked set to end her wait for a major title when she moved 3-0 up in the second.
Jelena Ostapenko had to save break points to avoid falling 4-0 behind in the second set after losing the first
A large contingent of Romanian fans was now chanting her name with confidence, but her run of six games in a row came to an end, and Ostapenko grabbed the momentum.
She tore into the Halep second serve, stepping inside the baseline and attacking off both sides, and her power was simply too much for her opponent's defence.
A forehand down the line brought up Ostapenko's 36th winner, and with it a huge roar from the captivated home crowd, as she drew level at one set all.
Halep took charge again early in the final set, getting the break at 3-1 after taking some pace off the ball and drawing an error, but again Ostapenko came straight back.
A fortunate net cord gave her the crucial break of serve at 3-3, prompting Halep's coach Darren Cahill to look to the sky in disbelief, but the Latvian was on a roll.
She stormed through the last five games in a row, apparently free of nerves, to clinch victory and grab her place among the elite of women's tennis.
"I always had the possibility I could hit the ball really hard. If I have a chance to go for a shot, I'm trying for it," Ostapenko said.
"Nobody taught me. It's just the way I play. And also I think my character is like that. So I want to really hit the ball."
'It is my dream, I'm so happy' - what they said
Jelena Ostapenko: "I cannot believe I am champion at 20 years old. I love you guys. It's so amazing to be here.
"I have no words, it is my dream. I'm so happy. I knew Simona was a great player, but I tried to play aggressively and everything turned my way. I fought for every point. I'm glad it finished my way."
Simona Halep: "I'm sad I couldn't win it, but it was a great experience.
"Now I want to congratulate Jelena - it's an amazing thing. Keep it going because you are only a kid.
"I would like to thank my team, my parents. It's a tough day, but let's keep working and let's believe.
"I felt sick in the stomach to play in this final, so maybe I wasn't ready to win it, but maybe next time."
Russell Fuller, BBC tennis correspondent:
"Ostapenko was a teenager before Thursday and had never previously featured in the second week of a Grand Slam.
"She was playing an opponent who had experienced the 2014 French Open final and was one win away from becoming world number one, and yet the 20-year-old seemed from the start to have the ability to control the match.
"She goes for broke and misses a lot, but when it really mattered - when she was a set and 3-0 down - she had the power and nerve to take the match away from Halep.
"Can she become a serial Grand Slam champion?
"Time will tell, but she certainly has the game and the presence of mind. She kept Halep waiting on the baseline for nearly a minute as she rearranged her towels and her bag at the start of the match."